Module 3 : MAGNETIC FIELD
Lecture 15 : Biot- Savarts' Law

\includegraphics{fig3.21.eps}

If the palm of the right hand is curled in the direction of the current, the direction in which the thumb points gives the direction of the magnetic field at the centre of the loop. The field is, therefore, outward in the figure shown.

Note that for $z\gg a$, i.e. the field due to circular loop at large distances is given by

\begin{displaymath}B = \frac{\mu_0 I a^2}{2z^3} = \frac{\mu_0\mu}{2\pi z^3}\end{displaymath}

where $\mu =I \pi a^2$is the magnetic moment of the loop. The formula is very similar to the field of an electric dipole. Thus a current loop behaves like a magnetic dipole.

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